Macronutrient Calculator

How to use the macro calculator

Choose US or metric units, then enter your age, sex, height and weight. The unit choice sets the height boxes and decides whether amounts are printed in ounces or grams; the weight box has its own kg / lb selector. Age and weight are required, and a blank height is counted as zero, so enter it.

Pick the activity level that matches a normal week, then choose a macro balance. The balances are written carbs / protein / fat as a share of your Calories, for example Moderate: 50 / 25 / 25. Press Calculate to see:

• Carbohydrates, Proteins and Fats: the daily amount of each, with the Calories it contributes in brackets.
• Total: the combined weight of the three nutrients per day.
• Calories: your estimated daily energy need, which is what the split is applied to.

In US units the carbohydrate line is shown in ounces to two decimals and the others in whole ounces, so for small portions it is easier to read the metric (gram) view.

How the split is calculated

First the calculator estimates your resting energy use with the Mifflin-St Jeor equation and scales it by your activity factor (1.2 sedentary, 1.375 light, 1.55 moderate, 1.725 high, 1.9 extreme). Then each nutrient receives its share of those Calories and the Calories are converted to weight using the energy in a gram of that nutrient.

carbohydrate g = Calories × carb share ÷ 4

protein g = Calories × protein share ÷ 4

fat g = Calories × fat share ÷ 9

Worked example. A 30-year-old man, 5 ft 10 in and 180 lb, exercises lightly and picks the Moderate balance (50 / 25 / 25). His BMR is 1,783 Calories, so his daily need is 1,783 × 1.375 = 2,451 Calories. Carbohydrate gets 50%, or 1,226 Calories and 1,226 ÷ 4 = 306 g. Protein gets 25%, or 613 Calories and 153 g. Fat gets 25%, or 613 Calories and 613 ÷ 9 = 68 g. The three weigh 528 g together, about 18.6 oz.

Compare that with the Keto balance (10 / 15 / 75) for the same man: about 61 g of carbohydrate, 92 g of protein and 204 g of fat. The Calories are identical; only the proportions, and therefore the foods on the plate, change.

Macros in common eating patterns

Here is how each preset in the calculator translates on a 2,000 Calorie day:

The DASH split follows the eating plan developed for blood pressure control, which is rich in vegetables, fruit, whole grains and low-fat dairy. The Zone diet aims for a 40 / 30 / 30 split at every meal. A ketogenic diet keeps carbohydrate low enough that the body produces ketones, a pattern also covered by the keto calculator.

Is there an optimal macro balance?

Health agencies describe a range rather than one ideal. The US National Academies give acceptable macronutrient distribution ranges of 45-65% carbohydrate, 10-35% protein and 20-35% fat for adults, and an allowance of 130 g of carbohydrate a day to fuel the brain. Only the Moderate and DASH presets above sit fully inside those ranges. The others trade one nutrient against another (less fat in High carb, less carbohydrate in Zone, Low carb and Keto), which is fine as a deliberate choice but not as an automatic default.

Beyond that, the best split is the one you can follow consistently. Endurance athletes training for hours a day need much more carbohydrate (sports dietitians quote anything from 3 to 12 g per kilogram depending on the load), strength athletes lean on protein, and people managing a medical condition may be given specific targets by their care team.

Check your protein on its own with the protein calculator, and your fat with the fat intake calculator.

Macros and weight loss

Whether you lose weight depends first on how many Calories you eat compared with how many you use. When researchers feed people controlled diets that differ in macro composition but match in Calories, fat loss ends up broadly similar. Macros still matter for the practical side of dieting: protein and fibre-rich carbohydrate make meals more filling, and enough protein helps preserve muscle in a deficit.

A common approach is to work out maintenance Calories with the TDEE calculator, subtract a moderate amount, then set protein first (often 1.6 to 2.2 g/kg for people who train), fat second (not less than about 20% of Calories), and fill the rest with carbohydrate. Use this calculator's Calories line as a reference point, and trim from there.

The idea behind "if it fits your macros" (IIFYM) is flexible dieting: any food is allowed so long as the daily totals land near target. It makes tracking easier, but the quality of the foods still decides how much fibre, vitamins and minerals you get.

What are macronutrients?

Macronutrients are the nutrients needed in large amounts that supply Calories: carbohydrate, protein and fat. (Alcohol also provides energy, at 7 Calories per gram, but is not a nutrient.) Vitamins and minerals are micronutrients; they provide no energy.

Cautions before you follow a macro plan

The Calorie figure is an estimate with a margin of error of several hundred Calories a day, and the presets are examples, not prescriptions. People who are pregnant or breastfeeding, under 18, living with diabetes, kidney disease or an eating disorder, or taking medicines affected by diet, should get individual advice from a doctor or registered dietitian. Very low-Calorie plans should be supervised. See the disclaimer.